WO2004057963A1

WO2004057963A1 - Aquatic admixture and distribution method

Info

Publication number: WO2004057963A1
Application number: PCT/NZ2004/000001
Authority: WO
Inventors: Mark Raymond Fabish
Original assignee: Mark Raymond Fabish
Priority date: 2002-12-28
Filing date: 2004-01-05
Publication date: 2004-07-15
Also published as: NZ512258A

Abstract

An admixture for distribution in an aquatic environment, characterised in that said admixture is formed as pellets, each including one or more constituents incorporated in a frozen solution, and a method of producing said admixture pellets comprising the steps of: forming said admixture by combining said constituents with said solution; transferring the admixture to one or more pellet moulds; subjecting said moulds to sub-zero temperatures in a rapid freezing apparatus; extracting the pellets from said moulds and transferring same to refrigerated storage prior to distribution over an aquatic area.

Description

TITLE: AQUATIC ADMIXTURE AND DISTRIBUTION METHOD

TECHNICAL FIELD

The present invention relates generally to a means for distributing an admixture to a chosen sub-surface depth in aquatic environments, and in particular to the distribution of fertiliser including nutrients and minerals.

BACKGROUND ART

Dwindling fish stocks are of worldwide concern and the subject of intensive research in an effort to maintain or increase catches without irreparable harm to sustainable fish numbers. Many regions historically renowned for high fish yields have been subjected to such intensive over-fishing that fish populations have been exhausted.

In an attempt to attenuate or even reverse such declining fish populations, several multi-national research experiments have been undertaken to add fertiliser to the oceans in an attempt to stimulate the localised eco-systems. The initial open-ocean fertilisation experiment of the Galapagos Islands in 1993 involved the single addition of half a tonne of iron filings over a 100 km² area. This resulted in a forty-fold increase in the phytoplankton over a 300 km² area. As phytoplankton forms a primary constituent of the food source at the base of marine eco-system pyramids, they are in turn eaten by numerous larger entities such as protozoa and zooplankton, which are in turn eaten by small carnivorous fish, which are naturally eaten by larger fish.

Similarly beneficial results were also attained in 1995 during a second experiment in the equatorial pacific, which again produced a phytoplankton bloom. A further benefit of such fertilisation is the increased levels of carbon dioxide absorbed by the ocean, to mitigate the effects of such greenhouse gases.

Nevertheless, these earlier fertilisation experiments possessed several shortcomings, namely:

- Although the fertiliser contained nutrients necessary for photosynthesis, respiration and other vital life processes, other equally critical nutrients

(such as silicon needed for skeletal growth) were omitted.

- Nutrients were only distributed on the ocean surface by mixing a solution including iron and sulphur hex (as a tracer) into the propeller wash. This lead to the iron congealing, causing it to be precipitated out of the surface water and sinking out of the sunlit depths where photosynthesis occurs.

- The increased food supply localised solely at the surface interfered with the diurnal movement and feeding cycle of the zooplankton, which normally migrates vertically at night from deeper water (200 m or more) to feed while the ambient light levels are low. It was found the zooplankton remained at the surface for several days after the fertilising, thus interfering with the feeding patterns of others in the food chain, which normally feed on the zooplankton at the lower depths during the daylight periods.

Many inland waterways such as lakes, rivers and fiords have become polluted over time from an influx of airborne and/or waterborne contaminants. This has given rise to highly acidified Scandinavian fjords, lakes and North American lakes that are currently treated with lime in an attempt to restore the correct pH levels of the water. However, it has been found that implementing liming by the cheapest method, i.e. to add the lime directly to the water body, can cause aluminium and other metals to come out of solution and fall to the bottom of the water body, causing toxicity issues. Although lime can be added to the catchment regions, to address this problem, it can have an adverse effect on adjacent wetland plants species and is less effective and economical. Surface applications of lime also increase the water cloudiness and turbidity. Each year in Sweden alone, thousands of tonnes of limestone are sprayed on acidified lakes and watercourses, by means of trucks, boats or helicopters costing millions of dollars.

Similarly, excessive algae growth in lakes and waterways is currently treated by spreading aluminium sulphate. Again, such methods give little control over the sub-surface distribution of the aluminium sulphate.

In instances where herbicides are used to control noxious weeds such as Lagarosiphon (or "oxygen weed"), it is even more critical that the distribution of the active material (i.e. the herbicide) does not harm other plant or animal life. It is thus desirable to improve the distribution control over these substances.

Conventional distribution methods are susceptible to the effects of water currents and other water flows that may not necessarily be evident from the surface. The monitoring of such water movements is also of interest in oceanography and the like, though this is difficult to perform due to the general uniformity of the water.

Any references cited in this specification are hereby incorporated by reference, though no admission is made that any reference constitutes valid prior art. The discussion of the references states what their authors assert, and the applicant reserves the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that any prior art publications referred to herein does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country. It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or

'comprising' is used in relation to one or more steps in a method or process.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description, which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided an admixture for distribution in aquatic environments, characterised in that

said admixture is formed as pellets, each including one or more constituents incorporated in a frozen solution.

Preferably, characteristic parameters of the pellets are varied to produce a frozen pellet with resulting neutral buoyancy at a predetermined depth.

Preferably said characteristic parameters of the pellets are varied to release said constituents at a predetermined depth or depth range.

According to one embodiment, said characteristic parameters include, but are not limited to, pellet weight; density; volume; shape; pH level; salinity; chemical, thermal, magnetic and/or electrical properties; internal and external temperature:, and construction.

When distributed over water, the frozen admixture pellets thus provide a means of placing the pellet constituents at a particular depth, governed by the relative buoyancy of the frozen pellet, its melt rate and the local water conditions, such as temperature, salinity, currents, light levels and so forth.

As used herein, the term 'aquatic ' includes any body of water and encompasses inland lakes, rivers, and other fresh-water bodies in addition to salt-water seas and oceans.

The term 'pellets' used herein is not restricted to any specific volumetric shapes and includes, but is not limited to, cubes, cuboids, spheres, oblate spheroids, rods, other multi-sided, asymmetric irregular shapes and any combination of same.

While cube-shape pellets may be readily produced and give predictable and consistent melt characteristics, the invention is not limited to same and alternate shapes may be employed according to the particular characteristics of the constituents, the freezing solution, and/or the desired aquatic, handling, manufacturing or storage performance of the pellet.

According to one embodiment, said constituents are selected from the group including (but not limited to) silica sand, iron, phosphorous, silicon, lime, calcite, calcium carbonate, aluminium sulphate, copper acetate, sulphur hexafluoride, sodium chloride and/or calcium chloride.

It will however be understood that alternative constituents may be utilised and these need not necessarily form a fertiliser or the like. Although particularly suited to the distribution of fertiliser, the present invention may also be used to distribute any other type of matter requiring distribution across a body of water and thereafter sink to a particular depth before being released. Alternatively, it may be desired to release the constituents continuously through a predetermined depth range as the pellet sinks. It is even possible for non-uniform pellets to be produced whereby (optionally different) constituents are release at different depths.

In some instances, it may be desired to slowly release the constituents at the surface (i.e. zero depth) and this may also be achieved using the present invention.

In alternative embodiments, the pellets may be configured to sink to the bottom surface of the water environment (e.g. the lake or seabed) to release the constituents.

The constituents may be incorporated into the frozen solution in any convenient manner, depending on the properties of the constituents, the manufacturing method employed and the constituents' release characteristics desired.

Thus, according to one aspect of the present invention, said incorporation of the constituents into said solution is by entrainment, dissolving, suspension, and/or encapsulation.

The constituents may, for example, be a fine particulate powder physically dispersed throughout the solution and then frozen in situ, or chemically dissolved into an appropriate solvent solution, or even remain as a solid core at least partially surrounded or encapsulated by a jacket of frozen solution.

Preferably, the silica sand is in an amorphous powder state and/or iron is dissolved into a solution of pure or distilled water. Optionally, said constituents further include phosphorous. The movements of the pellets after release into the water may be tracked, either to monitor the resulting dispersion of the constituents and/or as an end in itself to study the effects of currents, and other water movements

Thus, in a preferred embodiment, tracking of the pellets distribution and movement is enabled by the incorporation of at least one tracking element.

In one embodiment, said tracking element is configured to present a detectable reflection signal to electromagnetic or acoustic irradiation. In an alternative embodiment, said tracking element is configured to display an identifiable magnetic or electrical signature.

According to one embodiment, tracking elements are formed within the pellet as voids or air bubbles. This provides an inexpensive means of increasing the delectability of the pellets to sonar equipment (for example) without the need for costly specific high-reflectivity constituents. The sonar signature of the pellets may be varied by adjusting the number and/or size of the voids. Large voids may be molded within the pellet.

If higher degrees of detectability are required to register a signal with a particular sensor type, e.g. a magnetic anomaly detectors, then specific elements (e.g magnetic particles) may be added to the pellet as tracking elements.

If the study of the water movements is the sole purpose of the pellet release, it will be appreciated that all the constituents may be formed from harmless, inexpensive materials (e.g. frozen water with entrained bubbles) that may be dispersed without any environmental consequence.

In one embodiment, sulphur hexafluoride SF₆ is bubbled through said constituents in solution until saturated prior to freezing. The SF₆ acts as said tracking element enabling known monitoring techniques such as satellite, ship borne or airborne surveillance to track the effects or extent of the fertilisation distribution.

According to a further aspect of the present invention, the constituents and solution are agitated prior to freezing. This ensures a homogeneous dispersing of the constituents through the pellet.

Sodium chloride and/or calcium chloride may be added to the solution prior to freezing to alter a characteristic parameter of the pellet, i.e. the freezing temperature of the pellet solution, e.g., a solution of water and 21 % sodium chloride freezes at -18°C.

Although water (distilled or otherwise) provides an ideal solution in which to incorporate the admixture constituents, it will be appreciated that alternative fluids or even gases may be utilised. Furthermore, instead of being solely an inert transportation medium for the admixture constituents, solution itself may also be a constituent.

As used herein, the term 'admixture' includes compositions comprised of a single constituent and/or compositions where said solution is the sole constituent.

The frozen pellets may be formed and distributed by a variety of means.

According to one aspect of the present invention embodiment, said pellets are formed by a method comprising the steps:

- forming said admixture by combining said constituents with said solution;

- transferring the admixture to one or more pellet moulds;

- subjecting said moulds to sub-zero temperatures in a freezing apparatus, e.g. cryogenic or immersion freezing; - extracting the pellets from said moulds and transferring same to refrigerated storage prior to distribution over an aquatic area.

According to further embodiments, said method further includes the steps of:

storing said admixture in a storage container prior to transfer to said moulds;

- continuously agitating the admixture in said storage container;

- using sealable containers as moulds; and/or

applying a heated medium (e.g. hot air or water) to said moulds after freezing to aid pellet extraction.

The formed pellets are placed in refrigerated storage until required for application. Fertilising large regions of water is most practically accomplished using aircraft or watercraft as the means of deployment.

In oceanic fertilizing applications, the plant plankton being fertilised only survive for 2-3 days, while the animal plankton (zooplankton) that feed on the plant plankton live for 2-3 weeks. As a consequence of the brief lifespan of the plant plankton, fertilisation needs to be conducted regularly (e.g. every 3-5 days) and in order to consistently dispense the fertiliser pellets in the same zone, an accurate and rapid delivery means is required. Currently, this can most effectively be provided by an aircraft equipped with global positioning system (GPS) navigation equipment.

The precision of GPS-equipped aircraft permits the fertiliser to be evenly distributed over the target area without the risk of inadvertently over-fertilising a particular portion of the sea and possibly creating a bloom which would impair sea life due to the depletion of the water oxygen content. Ships may possibly be used in conjunction with, or instead of, aircraft in instances requiring small areas to be fertilised, or if the same target area requires continual re-fertilising.

According to a further aspect, the present invention provides a method of distributing an admixture substantially as described above to a target area of water, including the steps:

- storing said pellets in an insulated and/or refrigerated dispenser on a delivery platform,

- sweeping said target area in said delivery platform and dispensing said pellets in an even non-overlapping distribution pattern;

Preferably, said delivery platform is an aircraft, helicopter, or ship, preferably equipped with GPS navigation.

Preferably, characteristic parameters of the pellets are controlled to produce a frozen pellet with a resulting neutral buoyancy at a predetermined depth, preferably within a depth of 200 meters from the water surface of the target area.

Thus, in one embodiment, the pellets are manufactured to release their constituents at a particular depth and are dispensed over the target area, typically by an aircraft or watercraft. The frozen pellets then sink relatively rapidly until their relative buoyancy is neutral. During the sinking stage and thereafter, the pellet will start melting, thus releasing the stored constituents, such as the fertiliser iron and/or silica.

If sodium chloride or calcium chloride is used as a pellet constituent, the brine solution created upon melting will allow the pellet admixture once melted to remain as a fluid at temperatures below 0°C. Moreover, as this melted pellet solution is colder and denser than the surrounding water, it will sink below the remainder of the melting pellet and thus acts to further distribute the constituents. If a tracer (e.g. SF₆) is utilised, this is also released at this point by the melting pellet, which will allow the localised area of admixture-seeded water so created to be traced using modern satellite technology.

As previously discussed, the melting time is dependent upon surrounding water temperature, the size of the blocks and the internal temperature of the blocks, e.g. a block stored at -30°C and configured to sink to a depth of 50 m will melt at a different rate compared to a block configured to float on the surface and stored at -3°C. In applications where it is desired to release the constituents at a specific depth, an even and consistent melt may be achieved with a homogenous pellet, where the density remains approximately constant as the constituents continually dissolve into the water at the target depth

The fast freezing methods (cryogenic or immersion) used ensure the required density and homogenous distribution of the constituents throughout the entire pellet structure. This is an important point in aquatic fertilisation applications as the diatoms are poor swimmers and not very mobile in comparison to other planktonic life forms. Furthermore, as they are neutrally buoyant at best, the diatoms (the dominant plant plankton species requiring silica for skeletal growth) are not able to actively head to nutrients as easily as other competing species. This places a yet further premium on adequate distribution of nutrients through the entire sunlit layer where photosynthesis occurs. It can be seen therefore that the present invention transports the nutrients to the planktonic life more readily.

In some mountainous coastal regions such as Norwegian fjords or Fiordland in New Zealand, high rainfall can place a significant freshwater layer on top of the saltwater. This salinity disparity can present a penetration barrier to some conventional surface aquatic distribution methods. The present invention enables nutrients or any other chosen admixture to be distributed below the freshwater layer by appropriate configuration of each pellet's characteristic parameters, particularly density and melt rates.

The admixture pellets may also be used in a variety of additional applications.

In one embodiment, using silicon or phosphorous as constituents in the admixture can aid in establishing or maintaining an optimum composition of nutrients and plankton in seawater, in particular the Redfield ratio.

The 'Redfield ratio' or 'Redfield stoichiometry' refers to the molar ratio of carbon (C), nitrogen (N) and phosphorus (P) in phytoplankton (principally diatoms). When nutrients are not limiting, most phytoplankton has the molar ratio of C:N:P = 106: 16: 1. Achieving this ratio optimises the potential growth of the available aquatic life.

The present invention may also be used to vary the pH level of an aquatic environment such as lakes subjected to the effects of acid rain. By the application of lime as a constituent, the pH level of acidified lakes may be increased, with the lime being released at the desired depth and not just on the surface.

Liming is the addition of limestone (calcite), primarily calcium carbonate (CaCO₃), to neutralize acid waters and soils and buffer them from rapid fluctuations in pH.

Limestone can also be applied to lakes, ponds, fjords and their surrounding watersheds to protect them from acidification, to add calcium, and to restore their important ecological, economic, and recreational values. Adding limestone to maintain a near-neutral pH (pH 7) keeps water safe for aquatic life. Conversely, the pH level of alkaline water may be reduced if desired by using acidified constituents

Thus, according to a further aspect, the present invention provides a method of increasing or decreasing the pH level of an aquatic environment by the respective distribution of said pellets incorporating constituents of a correspondingly higher or lower pH level than said aquatic environment.

In one embodiment, the present invention provides a method of reducing the acidity of an aquatic environment by the distribution of said pellets including a constituent of lime.

Conventional methods of liming water bodies are by:

(1) Boat: The limestone is placed into the wake (prop wash) of a moving powerboat or in an alternative broadcast method, limestone slurry is distributed via a high-pressure water hose from a moving barge platform.

(2) Placement on winter ice: In regions with prevalent winter surface ice thick enough to support vehicles, the lime may be spread over the ice surface for distribution with the spring melt.

(3) Aircraft: Rapid, though expensive method compared to boat delivery.

(4) Watershed Distribution: Limestone applied by helicopter, truck, or hand within the water body watershed eventually washes into the water body, though at a greater cost in time and quantity of lime required.

Although these methods vary in cost and effectiveness, none can control the dispersal of the lime below the surface. Furthermore, it has been found in Scandinavia that direct application of lime to the water surface (methods 1-3), can cause aluminium and other metals to come out of solution and fall to the bottom of the water body, causing toxicity issues. Although Lime can be added to the catchment regions, this can have an adverse effect on adjacent wetland plants species and is less effective and economical than direct surface application. Surface applications of lime also increase the water cloudiness and turbidity.

The aforesaid disadvantages may be addressed by the present invention through the capacity to release the lime (as a pellet constituent) at the particular depths required (including on the lake bed surface itself) without being spread indiscriminately throughout all water depths. It also enables the quantity and release depth to be varied dependant on the total depth of the water. Thus areas of deep water having greater volumes may be provided with proportionally greater amounts of limestone.

In further embodiments, the present invention may be used to provide increased control over the release of algaecides and herbicides to combat aquatic weeds and the like. Many aquatic environments including lakes and rivers have experienced dramatic growth in the noxious, toxic or otherwise undesirable or overabundant aquatic plants. However, many aquatic herbicides and algicides used to control such plants are potentially harmful to many non-target plants, fish and/or humans and require strict usage control. Many of the usage restrictions and risks associated with such products may be attenuated by the ability to release the active agent at the optimum depth without prior dispersal through the intervening water depth.

The present invention not only provides the ability to release the algaecide or herbicide at a particular depth, it also enables the lateral dispersion of the algaecide/herbicide release to be controlled as it effectively originates from a point source i.e. the pellet. Thus, according to a further aspect of the present invention, there is provided a method of controlling noxious or unwanted aquatic organic growth by distribution of said pellets wherein at least one constituent is an algaecide or herbicide.

A further method of water treatment provided by the present invention is the reduction of algae growth either directly, or by the removal of phosphorus from the affected water.

Aluminium sulphate (alum) is widely used in the purification of waste water as well as water from rivers, lakes and reservoirs. It is a flocculating agent with the capacity to coagulate and trap solid matter that may be floating in the water, such as algae and other organic and non-organic matter.

The process produces a fine precipitate that removes many contaminants, including the spores of dangerous pathogens.

Thus, according to an aspect of the present invention, there is a provided a method of algal control by the distribution of said pellets wherein at least one constituent is aluminium sulphate.

According to a further aspect of the present invention, there is a provided a method of algal control by the distribution of said pellets wherein at least one constituent contains a substance capable of coagulating with phosphorus.

Phosphorous promotes both weed and algal growth and thus by providing a constituent of the admixture (e.g. aluminium sulphate) that upon distribution precipitates phosphorous from the water by coagulation or coalescence, both algal and weed growth may be reduced. It will be appreciated other constituents may be used to provide the same effect. In further applications, the present invention may be used to fight toxic aquatic blooms created by flagellates that can stray into regions of commercially sensitive aquaculture. Instead of using chemical or biological agents to combat the blooms, an alternate approach is to promote the growth of non-harmful sea life that can out-compete the toxic flagellates. This however requires the use of a substance that is only beneficial to the non-harmful organisms and not the toxic flagellates.

In one embodiment, there is provided a method of aquatic bloom control by promoting the growth of diatoms, said method including the distribution of said pellets wherein at least one constituent contains silica.

Silica is an essential requirement for the growth of diatoms which all have shelllike, brittle cell walls made out of silica (glass) and pectin. Thus, by increasing the silica available for growth, the indigenous diatoms are advantaged without benefit to the flagellates, and are thus able to compete more favorably for the same food source.

The present invention may also be utilised as a shark repellant, whereby an active shark-repelling agent such as copper acetate (a mixture of copper sulphate and acetic acid) is a constituent of the pellet admixture. The pellets may be deployed around swimming/surf areas on popular beaches, or around competition areas during triathlons and the like.

A variety of distribution methods may be employed, such as being broadcast over the whole of the protected area from a boat platform, or released periodically from dispensers tethered about the periphery of the protected area.

Pellets may be configured to continuously release the shark repellant mixture as they descend giving a 'curtain' effect. Alternatively, batches of pellets configured to release the repellent at differing depths may be released either simultaneously or according to a predetermined sequence to give the protection desired.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the ensuing description, which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a schematic representation of a manufacturing and distribution system of an admixture according to an embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Figure 1 shows a schematic representation of a first embodiment of the present invention, comprising generally of a pellet manufacturing process (1 ) and subsequent distribution system (2).

It will be appreciated the embodiment illustrated is purely exemplary and the invention is not restricted solely to the embodiment shown.

The manufacturing process (1 ) is comprised of a storage vat (3) containing an admixture of one or more constituents. In a preferred embodiment, the constituents form a fertiliser comprised of silica sand (as found in an amorphous state), iron (dissolved in pure /distilled water), and/or phosphate (suspended in a water solution) combined in a water solution. Sodium chloride or calcium chloride may optionally be added to adjust the freezing characteristics of the admixture. An inert gas sulphur hexafluoride (SF₆) is bubbled through the admixture solution until it becomes saturated. The admixture is then agitated to ensure a homogenous distribution of the constituents in a fine suspension. It will be appreciated alternative constituents may dissolve completely in an appropriate solvent, or become entrained in a more viscous solution.

The admixture is poured into a series of moulds (4) in the form of sealable stainless steel containers and placed on a conveyor track (5) and transported to a rapid freezing chamber (6). The rapid freezing process may be achieved by the known techniques of cryogenic freezing or immersion. Both techniques are well known in the food industries and provide a more rapid freezing than conventional blast freezing.

In blast freezers, fans blow and circulate cold air (normally minus 25 to minus 40°F) over a product that has been placed in trays or on racks carried on conveyor belts through a horizontal tunnel or vertically in an ascending spiral. Cryogenic freezing is an advanced, accelerated form of blast freezing in which products are exposed to very cold air or, more commonly, to sprays of liquid nitrogen or carbon dioxide at temperatures of minus 150 degrees F or colder.

Alternatively, the moulds are immersed in a liquid refrigerant in the freezing chamber (6) and again this results in an extremely rapid freezing of the admixture due to the high thermal transfer from the admixture to the refrigerant. In the food industry, rapid freezing is desirable to minimise food degradation and to maintain freshness. In the present invention, the rapidity of the freezing process ensures the admixture constituents are frozen with a homogenous distribution through the solution. The moulds (4) are then transferred to a mould extraction apparatus (7) where heated air or fluids are applied to the moulds to aid in detaching the admixture

(now in the form of a frozen pellet (8)) from the mould (4). It will be clear the size and shape of the pellet (8) will be determined by the corresponding size and shape of the mould (4) and that numerous configurations are readily achievable.

After extraction from the moulds (4), the pellets (8) are placed in a refrigerated cool store (9) until required.

In use, the pellets (8) are placed in storage containers (10) onboard one or more delivery platforms depicted by aircraft (11). It will be appreciated that the choice of delivery platform used is flexible and may be chosen according to the logistical and economic factors germane to the particular application. The size and configuration of the storage container (10) will be governed by the size of the target area (12) to be fertilised and total flight distance involved. Simple insulated containers (10) may be employed for short flights, while longer flights require the container (10) to be refrigerated to maintain the pellets (8) in their correct state.

It will be appreciated that numerous configurations of dispersal equipment (not shown) may be utilised on the aircraft (11) to dispense the pellets (8) from the container (10), including dispensing directly from the container (10) itself, to using a hopper (not shown) into which the containers (10) are successively emptied. If helicopters (not shown) are used, the container (10) may take the form of a bucket or hopper slung beneath the craft.

The aircraft (11 ) sweeps the target deployment area (12) to dispense the pellets (8) using GPS navigation to avoid overlapping sweeps and to co-ordinate successive flights to the same target area (12). In one embodiment, the above-described invention is applicable to fertilising sub- Antarctic regions of the southern ocean or other comparable regions found to be deficient in nutrients of some form, e.g. silica required for skeletal growth of Diatoms, the dominant plankton species, .

After release, the pellets (8) sink until neutrally buoyant to a particular depth within the phototrophic layer (13). This depth (which may be zero, i.e. the surface) is a result of characteristic parameters of the pellets defined during manufacture, including the pellet weight, density, volume, internal and external temperature, and construction. These parameters may be varied to suit the localised condition in the target area (12) including the water temperature, salinity, the presence of diurnal, seasonal and permanent thermoclines and any other germane environmental factors.

The incorporation of sodium chloride or calcium chloride in the pellets (8) enables the salinity of the melting pellet to be varied to penetrate such thermoclines and permit the fertiliser to be dispersed at any desired depth within the sunlit depths where photosynthesis occurs. The sulphur hexafluoride tracer (if incorporated during manufacture) is released during melting to provide a means of tracking the location of the fertiliser deployment and can be detected down to a concentration of 10^~16 M.

As previously stated, the above-described embodiment of fertilising portions of the ocean is by way of example only. The present invention may also be used to distribute other admixtures e.g. aquatic herbicides, algicides, poisons, gelling agents, dyes or markers, electrically conductive particles, de-oxygenating or oxygenating substances, growth inhibitors, shark repellant or any other substance needed to be placed at particular depths over portions of a body of water. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims

CLAIMS:

1. An admixture for distribution in an aquatic environment characterised in that said admixture is formed as pellets, each including one or more constituents incorporated in a frozen solution.

2. The admixture as claimed in any one of the preceding claims, wherein characteristic parameters of the pellets are varied to produce a frozen pellet with resulting neutral buoyancy at a predetermined depth.

3. The admixture as claimed in claim 1 or claim 2, wherein characteristic parameters of the pellets are varied to release said constituents at a predetermined depth or depth range.

4. The admixture as claimed in claim 2 or claim 3, wherein said characteristic parameters include pellet weight; density; volume; shape; pH level; salinity; chemical, thermal, magnetic and/or electrical properties; internal and external temperature:, and construction.

5. The admixture as claimed in any one of the preceding claims, wherein said constituents are selected from the group including silica sand, iron, phosphorous, silicon, lime, calcite, calcium carbonate, aluminium sulphate, copper acetate, sulphur hexafluoride, sodium chloride, calcium chloride, aquatic herbicides, algicides and/or any combination of same.

6. The admixture as claimed in any one of the preceding claims, wherein said incorporation is by dissolving, entraining, suspension, and/or encapsulation.

7. The admixture as claimed in claim 5 or claim 6, wherein the silica sand is in an amorphous powder state.

8. The admixture as claimed in any one of the preceding claims, wherein said solution is a constituent.

9. The admixture as claimed in any one of the preceding claims, wherein the pellet is configured such that the constituents are released continuously through a predetermined depth range as the pellet sinks.

10. The admixture as claimed in any one of the preceding claims, wherein the pellet is configured such that different constituents are released at different depths.

11. The admixture as claimed in any one of claims 2-10, wherein said predetermined depth is within 0-200 metres inclusive from an upper water surface of the aquatic environment.

12. The admixture as claimed in any one of claims 2-10, wherein said predetermined depth is a terrestrial bottom of the aquatic environment.

13. The admixture as claimed in any one of the preceding claims, wherein said incorporation of the constituents into said solution is by entrainment, dissolving, suspension, and/or encapsulation.

14. The admixture as claimed in any one of the preceding claims, wherein said constituents are in the form of a fine particulate powder physically dispersed throughout the solution and then frozen in-situ

15. The admixture as claimed in any one of claims 1-14, wherein said constituents are chemically dissolved into a solvent solution.

16. The admixture as claimed in any one of claims 1-14, wherein said constituents remain as a solid core at least partially surrounded or encapsulated by a jacket of frozen solution.

17. The admixture as claimed in any one of the preceding claims, wherein each pellet incorporates at least one tracking element.

18. The admixture as claimed in claim 17, wherein said tracking element is configured to present a detectable reflection signal to electromagnetic or acoustic irradiation.

19. The admixture as claimed in claim 17, wherein said tracking element is configured to display an identifiable magnetic or electrical signature.

20. The admixture as claimed in claim 17 or claim 18, wherein said tracking elements are formed within the pellets as voids or air bubbles.

21. The admixture as claimed in claim 17, wherein said tracking element is sulphur hexafluoride (SF₆) bubbled through said constituents in solution until saturated prior to being frozen.

22. The admixture as claimed in any one of the preceding claims, wherein the constituents and solution are agitated prior to freezing.

23. The admixture as claimed in any one of the preceding claims, wherein said solution is pure or distilled water.

24. The admixture as claimed in any one of the preceding claims, wherein said admixture is comprised of a single constituent.

25. The admixture as claimed in claim 25, wherein the solution is said sole constituent.

26. A method of producing admixture pellets as claimed in any one of claims 1-25, said method comprising the steps:

forming said admixture by combining said constituents with said solution;

transferring the admixture to one or more pellet moulds;

subjecting said moulds to sub-zero temperatures in a rapid freezing apparatus;

extracting the pellets from said moulds and transferring same to refrigerated storage prior to distribution over an aquatic area.

27. The method as claimed in claim 26, further including the steps of:

storing said admixture in a storage container prior to transfer to said moulds, and

agitating the admixture in said storage container.

28. The method as claimed in claim 26 or claim 27, wherein said rapid freezing apparatus is a cryogenic or immersion freezing apparatus.

29. The method as claimed in any one of claims 26 - 28, further including the steps of:

using sealable containers as moulds, and

applying a heated medium to said moulds after freezing to aid pellet extraction.

30. A method of distributing an admixture as claimed in any one of claims 1- 25 to a target area of water, including the steps of: - storing said pellets in an insulated and/or refrigerated dispenser on a delivery platform,

- sweeping said target area with said delivery platform and dispensing said pellets in an even non-overlapping distribution pattern.

31. The method as claimed in claim 30, wherein said delivery platform is an aircraft, helicopter, ship or shore-mounted dispenser.

32. The method as claimed in claim 31 , wherein said delivery platform navigates said sweeping of the target area by use of GPS navigation equipment.

33. A method of increasing the harvestable yield of aquatic life in a target area including the steps of;

- distributing a plurality of pellets as claimed in claims 1-25 to the target area,

- harvesting a portion of said increased aquatic life.

34. The method as claimed in claim 33, wherein said pellets are produced according to the method claimed in claims 26 - 29.

35. The method as claimed in claim 34, wherein said pellets are distributed by the method claimed in claims 30 - 32.

36. A method of increasing or decreasing the pH level of an aquatic environment in a target area by the distribution of pellets as claimed in any one of claims 1-25 to the target area, said pellets respectively incorporating constituents of a correspondingly higher or lower pH level than said aquatic environment.

37. The method as claimed in claim 36, wherein said method reduces the acidity of an aquatic environment by the distribution of said pellets including a constituent of calcium carbonate.

38. A method of controlling noxious or undesirable aquatic organic growth in a target area by distribution of pellets as claimed in any one of claims 1- 25 to the target area, wherein at least one constituent of said pellets is an algaecide or herbicide.

39. A method of algal control in a target area by the distribution of said pellets as claimed in any one of claims 1-25 to the target area, wherein at least one constituent is aluminium sulphate.

40. A method of algal control in a target area by the distribution of said pellets as claimed in any one of claims 1-25 to the target area, wherein at least one constituent contains a substance capable of coagulating with phosphorus

41. A method of aquatic bloom control in a target area by promoting the growth of diatoms, said method including the distribution of pellets as claimed in any one of claims 1-25 to the target area, wherein at least one constituent contains silica.

42. A method of shark repelling in a target area, said method including the distribution of said pellets as claimed in any one of claims 1-25 to the target area, wherein at least one constituent is a shark-repelling agent.

43. The method as claimed in claim 42, wherein said shark-repelling agent is copper acetate.

44. The method as claimed in any one of claims 33 - 43, wherein said pellets are released by dispensers tethered to the periphery of said target area. ^•

45. The method as claimed in any one of claims 33 - 44, wherein said pellets are released by dispensers tethered in said target area.

46. A method of water flow monitoring in a target area by the distribution of said pellets as claimed in any one of claims 1-25 to the target area, irradiating the pellets with electromagnetic or acoustic radiation, and detecting a reflected signal from the pellets. .

47. The method claimed in any one of claims 36-46, wherein said pellets are produced according to the method claimed in claims 26 - 29.

48. The method as claimed in any one of claims 36-43, or 46 wherein said pellets are distributed by the method claimed in claims 30 - 32.

49. An admixture substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.

50. A method of producing an admixture substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.